Added btc_tracker.py and letter about Flask and threading.

letters/Flask_and_backend_process.py

@@ -0,0 +1,62 @@
+from flask import Flask
+import threading
+import sqlite3
+
+app = Flask(__name__)
+
+# Create a lock for synchronizing access to the database
+lock = threading.Lock()
+
+def my_background_process():
+    # Acquire the lock
+    lock.acquire()
+
+    # Connect to the in-memory database
+    conn = sqlite3.connect(':memory:')
+    c = conn.cursor()
+
+    # Create a table in the database
+    c.execute("CREATE TABLE mytable (col1 INTEGER, col2 TEXT)")
+
+    # Write to the database
+    c.execute("INSERT INTO mytable (col1, col2) VALUES (?, ?)", (value1, value2))
+    conn.commit()
+
+    # Close the connection
+    conn.close()
+
+    # Release the lock
+    lock.release()
+
+@app.route('/')
+def read_from_database():
+    # Acquire the lock
+    lock.acquire()
+
+    # Connect to the in-memory database
+    conn = sqlite3.connect(':memory:')
+    c = conn.cursor()
+
+    # Read from the database
+    c.execute("SELECT * FROM mytable")
+    rows = c.fetchall()
+
+    # Close the connection
+    conn.close()
+
+    # Release the lock
+    lock.release()
+
+    # Return the rows to the client
+    return rows
+
+if __name__ == '__main__':
+    # Create a new thread for the background process
+    thread = threading.Thread(target=my_background_process)
+
+    # Start the thread
+    thread.start()
+
+    # Start the Flask app
+    app.run()
+